The present invention was made during the designing of a ring-dye laser system for spectroscopic use. In accordance with the main objectives of the invention, an optical output coupler for lasers provides variable output coupling and simultaneous tunability without angular deviation, with all laser beams at Brewster's Angle. The device can be used with pulsed or continuous wave lasers.
No known variable output coupling devices with all the qualities described above exist in the prior art. Output coupling mirrors do not provide variable coupling. Birefringent tuners provide tuning without providing output coupling. Other prism methods provide tuning but not output coupling. Mirrors require changing when going from one wavelength to another. Dielectric coatings on optical components are susceptible to damage at high powers. Birefringent tuners are extremely expensive with the above-stated limitation.
The device in accordance with the present invention possesses, among others, the following advantages:
(1) The transmission coefficient can be changed in a controlled manner to obtain the maximum laser output or desired light flux within a cavity.
(2) There is negligible angular deviation of the output beam as the laser is tuned in wavelength.
3. Losses through undesirable reflections, scattering and absorption are minimized.
(4) The coupler can be used over the entire wavelength range for which the glass (or other material) used for the prisms has a low absorption.
(5) The possibility for damage is minimized even at high powers since no dielectric coatings are employed.
The novelty of the present invention over the prior art is believed to reside in the use of two Pellin-Broca prisms for obtaining variable output coupling from the laser systems. Novelty also is present in that the device achieves variable transmission through an output coupler, while simultaneously providing tuning capability for a tunable laser system without producing any angular deviation of the output, or losses due to unwanted reflections.
Other features and advantages of the invention will become apparent to those skilled in the art during the course of the following detailed description.